As stored program-controlled switching systems have evolved, a wide variety of useful features have been developed to extend the communication capabilities such systems provide. This development is expanded with the deployment of integrated service digital network (ISDN) switching systems which provide a separate, out-of-band signaling channel (the D-channel) between the switching system and ISDN customer stations.
When a customer orders ISDN service, the customer conveys to a telephone company representative the specific services desired, including bearer capabilities, supplementary services, etc. A significant part of this information is related to the assignment of the services, directory numbers, and call appearances to specific locations, e.g., buttons and lamps, on the ISDN stations. The customer may make these determinations by consulting a template and then verbally communicating which button is to activate each service and which lamp should be associated with each service. All of this information is then stored in the switching system database. In the past, it has been necessary to also manually enter into each customer station some of the information verbally provided to the representative. For the service to work properly, the station related information in the switching system must exactly match the information entered into the station.
To improve this process, a procedure known as ISDN parameter downloading has been proposed where the D-channel is used for downloading such station related information. With parameter downloading in place, the customer would communicate the desired service information to the telephone company representative as before. However, the customer stations would automatically request parameter downloading as part of their initialization procedure so that no additional manual steps would be required at the stations. When service profile changes occur in the switching system that require parameters to be downloaded again, the switching system notifies the customer stations to request a parameter download. Parameter downloading eliminates the time-consuming and error-prone manual steps at the customer stations.
A configuration group is a group of customer stations that are all identically configured, i.e., the buttons and lights are used in the same way for the same feature set. Corporate customers may each have one or more configuration groups that comprise hundreds or thousands of customer stations. The parameters for a particular configuration group are stored in a single storage location within the switching system for downloading to all customer stations of the group. When a change is made to a configuration group--adding the call forwarding feature, for example--a large number of stations are affected. Performing all the resulting notification and downloading in an uncontrolled fashion would unacceptably interfere with the switching system processing of telephone calls. The notification and downloading is further complicated because some of the stations may be in an inactive or out-of-service status at the time of the change to the configuration group.